A variable air volume (VAV) environmental management or air conditioning system modulates the amount of air that flows to different offices or locations within an environment such as an office building or other dwelling structure where numerous people live or work. By maintaining constant the temperature that flows through dampers of the air conditioning system and, instead adjusting the position of the damper or the volume of air that flows through the damper to the various locations within the environment, is possible to more efficiently and effectively address the comfort needs of different locations within the environment.
Known VAV controllers are large remote electronic boxes or cabinets that electrically connect to actuator motors that control the position of the dampers of the environmental control system. These controllers are often, for example, pneumatic controllers or electrical controllers that respond to temperature input to adjust the position of the damper in response to the sensed temperature of the various locations. These pneumatic drives or electrical systems are generally not inter-related from one location to another within the environment. As a result, compensating for temperature differences in one location frequently generates air flow problems in other locations within the environment. The air conditioning system, in these instances, operates in less than an ideal mode.
In recent years, microprocessors have been used to improve the efficiency of controlling various locations within the office or environment. These microprocessors attempt to relate locations within the environment to one another by using an air velocity pickup probe input. The air velocity pickup probe provides an input to the microprocessor that permits the microprocessor to compensate for drops in air flow to one location that arise from an increase in air flow to another location. In other words, microprocessor-based VAV terminal controllers attempt to improve the overall operation of the environmental management system by compensating for drops in air flow that occur as temperature needs or setpoints change at different locations within the environment. There are, however, significant limitations that associate with existing microprocessor-based VAV terminal controllers.
Significant limitations of existing microprocessor-based VAV terminal controllers are, for example, that the systems are bulky and include large printed circuit boards that mount within separate controller chassis. These known systems include motors and wires to control the damper motor in the environmental control system. In addition, existing microprocessor-based controllers at best use local area network technology for system data communication. Local area networks, however, are not designed for communicating control system data within a control system architecture. These local area networks inefficiently communicate temperature, pressure and other variable values from one location to another and to a central file server.
Another limitation associated with existing microprocessor-based VAV terminal controllers is the use of complicated instruction sets for generating the desired damper actuator control signal. For example, even the most efficient VAV terminal controllers use a control algorithm known as a proportional integral differential (PID) algorithm to drive the damper motor. The PID algorithm itself is complex and requires significant computational resources to generate the desired damper motor operating signal. The complexity of the PID algorithm requires significant setup time for each of the locations within the office or commercial environment. The setup time and inherent complexity of the algorithm makes such systems prone to error and highly susceptible to less than optimal performance.
Consequently, there is a need for an improved microprocessor-based VAV terminal controller that avoids the space requirements and separate bulky controller circuit chassis of existing microprocessor-based VAV terminal controllers.
There is a need for an improved microprocessor-based VAV terminal controller that is more effectively operable with other aspects of the environmental management system as well as with the VAV air conditioning system within the environmental management system.
There is yet the need for an improved VAV terminal controller that is simple to setup and use and that avoids the complexity of existing microprocessor-based controllers that use PID control instructions or other similarly complicated instructions to adjust for the differences in air flow within the air conditioning portion of the environmental control system.